Butterfly valves are commonly used to isolate and/or regulate flow of fluids, such as gases. In operation, a butterfly valve employs a rotatable disk, also referred to as the “butterfly” of the valve, which is positioned proximate to the center of a pipe or bore of the valve. The disk of the butterfly valve may be rotated by turning a shaft of the valve, with which the butterfly is, generally, operably associated. Rotation of the shaft by an outside actor (e.g., shaft rotation by an operator, shaft rotation via a crank, shaft rotation via an actuator, etc.) then causes rotation of the disk within the pipe or bore of the valve.
During use, the valve may be nearly fully opened when the disk is substantially parallel to the fluid flow of the valve and the valve may be nearly fully closed when the disk is substantially perpendicular to the flow of the valve. Accordingly, the butterfly valve can go from maximum flow capacity to minimum flow capacity with a quarter-turn (90 degrees) of the shaft.
In prior known butterfly valves, the disk may be oval in shape to maintain the shaft's placement within the valve relative to the bore, as the general oval shape can cause contact with the bore to prevent further shaft displacement. However, the shaft placement in such designs may be susceptible to inconsistent placement and/or may produce undesirable friction on one or both of the disk and the bore due to the contact. Therefore, improved butterfly valves which provide for consistent shaft and disk placement, relative to the bore, are desired.